1. Field of the Invention
The present invention relates to a post-processing apparatus for aligning a recording sheet where an image is recorded or performing a staple work, and more particularly, to a post-processing apparatus having a sheet end alignment member for carrying (pulling) a recording sheet to a sheet end position determination portion in order to align end edges of the recording sheets received in a compile tray.
2. Description of the Related Art
Conventionally, a post-processing apparatus for containing recording sheets where an image is recorded, aligning the recording sheets, binding the recording sheet bundle aligned in the compile tray with a stapler, and ejecting the recording sheet bundle according to a command of a user has been known.
In the post-processing apparatus, in order to align sheet carrying direction end edges of the recording sheets, a sheet end position determination portion (a sheet end position determination wall) is provided to a compile tray, the recording sheets collide with the sheet end position determination wall by using a paddle (sheet end alignment member) which is driven to rotate, so that the end edges can be aligned, and the sheets can be aligned in the width direction thereof by using a tamper (a sheet side edge alignment member) (for example, JP-A-10-120276). In addition, a post-processing apparatus having plural sheet end alignment members in accordance with positions of ejected sheets or a shape of the compile tray has been known.
In JP-A-2003-276933 ([0050] to [0054], FIG. 5), there is disclosed a post-processing apparatus including a first sheet end alignment member (knurling belt 191) disposed in a vicinity of a sheet end position determination wall (a collision supporting surface 131a) to enable the recording sheets to collide with the sheet end position determination wall and a second sheet end alignment member (inducing paddle 160) for pulling recording sheets ejected by an ejecting roller 7 into the first sheet end alignment member (knurling belt 191).
In JP-A-2003-276933, the second sheet end alignment member is driven to rotate at a predetermined position in a predetermined time according to received recording sheets. Therefore, if the sheet number of the recording sheets contained in the compile tray increases, a distance between the second sheet end alignment member and the recording sheet on the top surface of the recording sheet bundle is reduced, so that there is a problem in that a contact pressure increases and a carrying force in a sheet end alignment direction excessively increases. If the carrying force in the sheet end alignment direction, there is a problem in that paper alignment in sheet width direction by using a tamper is not sufficiently made, or there is a problem in that the recording sheets are bended.